This invention relates to a laminar electrical component and more particularly to wafer capacitors, multi-dielectric layer capacitors, and printed circuit assemblies all of which employ ceramic dielectric bodies that are comprised mainly of magnesium orthoborate.
It is well known to employ borate fluxes mixed with dominant quantities of a high firing ceramic to make dielectric ceramic bodies as is exemplified in my patents U.S. Pat. Nos. 3,885,941 issued May 27, 1975 and 4,027,209 issued May 31, 1977; and which is further exemplified in patents to I. Burns U.S. Pat. Nos. 4,101,952 issued July 18, 1978 and 4,308,570 issued Dec. 29, 1981. These four patents are assigned to the same assignee as is the present invention. However, all of the borate fluxes having been used as sintering aids in the prior art with the exception of several of the sintering aids claimed in my patent U.S. Pat. No. 4,533,974 issued Aug. 6, 1985 are glasses rather than being crystalline and they have a melting temperature less than the characteristic minimum sintering temperature of the high firing ceramic with which they are mixed to serve as a sintering aid.
The addition of these low melting glass fluxes reduces the temperature necessary for sintering by providing a vehicle for a liquid phase sintering mechanism. The only known exception to this behavior is produced by crystalline cadmium silicates which is described in my patent U.S. Pat. No. 4,266,265 issued May 5, 1981 and assigned to the same assignee. But of course, this flux is not a borate and there is no theory or key, by which such a crystalline compound that will be useful as a sintering aid or flux, will be recognizable.
It is also capable of being "fluxed" with high melting materials like barium oxide. It is the reaction of the boron in the magnesium orthoborate in a limited surface reaction with the "flux" to produce a eutectic and leading to liquid phase sintering at temperatures well below the melting point of either the "flux" or the magnesium orthoborate. For no other high firing dielectric than magnesium orthoborate is this known to be true.
Furthermore, the compound of central interest here, magnesium orthoborate, is a very obscure material. Except for its having received academic attention as one of the three single phase magnesium borates, it has apparently found no use.
It is an object of this invention to provide useful laminar electrical components having a dielectric ceramic body comprised predominantly of magnesium orthoborate.
It is a further object of this invention to provide a very dense, high Q and high frequency ceramic with a low dielectric constant as a dielectric body in laminar electrical components such as wafer capacitors, monolithic capacitors, and printed wiring substrates.
It is yet a further object of this invention to provide such components that are capable of being made by a process including cofiring the ceramic and metal elements.
It is still a further object of this invention to provide such components that incorporate base metals and may be sintered in a reducing atmosphere.
It is even a further object of this invention to provide such components that further include other high firing ceramic materials without exhibiting cracking and delamination after co-sintering.